The present disclosure relates to emulsion aggregation (EA) processes via a series of controllable contiguous or non-contiguous tank reactors for producing toner particles of desirable properties.
Processes for forming toner compositions for use with electrophotographic print or copy devices have been previously disclosed. For example, methods of preparing an emulsion aggregation (EA)-type toner are known and toners may be formed by aggregating a colorant with a latex polymer formed by batch emulsion polymerization. For example, U.S. Pat. No. 5,853,943, the disclosure of which is hereby incorporated by reference in entirety, is directed to a semi-continuous EA process for preparing a latex by first forming a seed polymer. Other examples of EA processes for the preparation of toners are illustrated in U.S. Pat. Nos. 7,785,763, 7,749,673, 7,695,884, 7,615,328, 7,429,443, 7,329,476, 6,830,860, 6,803,166 and 6,764,802, the disclosure of each of which hereby is incorporated by reference in entirety.
Batch processes for producing resins may be subjected to bulk polycondensation polymerization in a batch reactor at an elevated temperature. The time required for the polycondensation reaction can be long, due to heat transfer of the bulk material, high viscosity and limitations on mass transfer. The resulting resin then is cooled, crushed and milled prior to being dissolved in a solvent. The dissolved resin can be subjected, for example, to a phase inversion process where the resin is dispersed in an aqueous phase to prepare latexes. The solvent then is removed from the aqueous phase by a distillation method.
The use of solvents in such process causes environmental concerns. For example, if the solvent level is not low enough (<50 ppm), extensive waste water treatment and solvent remediation may be required.
In addition, where a batch process is utilized for aggregation and/or coalescence process, because the individual batch process involves the handling of bulk amounts of material, each process may take many hours to complete before moving to the next process in the formation of the toner particles. Batch-to-batch consistency can be difficult to achieve because of the number of and quality of reagents, the reactions and the conditions.
Wax often is included in toner, for example, to assist in the transfer of materials during the image-forming process. However, the transfer of materials depends, in part, on charge at the toner surface. Wax can have a negative impact on toner charge when present at the toner surface. Hence, toner with reduced wax content is beneficial.
Gloss can be controlled by fuser temperature, a variable that may change with run rate as well as environmental and use conditions. To overcome those variables, flat and/or wide gloss vs. temperature curves are preferred since such data and properties indicate variations of fuser roll or belt temperature on print image quality are minimized Such material is referred to as having wide fusing latitude.